Rotary drill stabilizer



Oct. 23, 1951 c. c. BROWN ETAL ROTARY DRILL STABILIZER Filed Sept. 9,1946 INVENTOR. rcera C Bmrwg Fred A M/rerm Irv ATTORNEY 'I l-1isinvention relates Patented Oct. 23, 1951 UNITED STATES A'l ENT OFFlC A 207. ROTARY DRILL STABILIZER Cicero O.-Brown and Fred F..Waltermire,Houston, Tex.

Application September 9, 1946, Serial No. 695,638

sections joined together by threaded couplings,

commonly called tool joints, the outside diameters :of 'Whicharesomewhat larger thanthat of thedrill pipe, but alsoof' substantiallyless'er' diameter than the bit and bitst m: andthe 'usual Kellyjoint andswivel attached to the upper end of the string, the kelly passingthrough'the'r'o tary table'and being rotated thereby in order to rotatethe drilling stringand bit; Such "drilling strings are extremelyflexible and elastic, particularly-when they have attained considerablelength due to deepening of the well. Due tothi's flexibility andelasticity,-it-is gen rally necessary toadd' weight to the bit in orderto keep the'bit in contact with the earth formation to enable it todrill ahead as'it-is rotated from the top of 1 the well:--- Toincrease-the weight'of the'bit. a section of pipe, commonly termed-a-'drill collar, isnormally interposed between the upper 'end of thebitstem andthe firstsectionofthe drill pipe. Such drill collars aregenerally of the same outsidadiameter as the bit stem and may vary inlength -very considerably, depending primarily upon the depth ofthe wellat a particulartime; These-drill collars may comprise asingle section ofpi e or several-sections. depending upon the 1 length desired. Forthepurnoses of this descriptionthe bit, bit stem and drill collars,together,

are sometimes herein-referred to as the bit section.

' Although the employment of drill collars helps to. stabilize theaction of the drill bit; nevertheless, because its diameter mustnormally be less than the over-all diameter of the-bit and of the holebeing drilled thereby, a substantial degree of clearance necessarilyresults between the out- 1 side of the drill collar and the wall of thewell; with the result that some degree of-"eccentricity or gyration'ofthe upper end particularly of the drill. collar occurs-during drillingandfrequently results inthe drilling or crooked holesy-and cavi :1

tation -in th'e'sides of the bore hole where the upper end of the drillcollar strikes the wall 2 Claims. (01. 255-28) under the eccentric orgyratory action mentioned. A further difficulty'which frequently.occurs, particularly in drilling deep wells with rotary drill" stringsof the type described, .arises from the combination of the gyratoryaction of the. bit section, the varying hardness of the formations beingdrilled, the fiexibilityand e'lasticityof the drill string, the rotationthereof, and improper applicationof the weight on'thebit. Thiscombination 'of conditions frequently'jcauses the bit .to changedirection .andidep'art from the. true vertical; Often this'diversion indirection is con tinuous and the well bore will be drilled atasubstantial angle to the vertical such that; when this condition isdiscovered, the drill string must be withdrawn to the point of departureof the orig.- inal bore hole from the vertical and 'by the use ofsuitable 'well known drilling tools,.the .well must he redrilled tostraighten 'out'the hole. On the other hand, the deviation from thevertical may be only temporaryand the bit may, either by controlof thedrilling operations or of its own accord, return to the originalverticaldirection after a relativelyshort length of'hol'e has beendrilled. i The common result 'of. such a temporary deviation is alateral'bend in the bore hole to which, the flexible drill string willgenerally accommodate itself without undue difficulty. However, due to,the flexibility and elasticity of the drill string, the section of thedrill string passing around such a curvedp'ortiori'of the hole, since itis normally under a substantial de ree of tension, will engage in aWhipping action laterally relative to the vertical axis of the boreholeand this action will cause the section of the drill pipe andany'tool joint thereon at this point to cut a vertical slot in thesideof the formation along the curved portion of the bore hole until itattains a lateral depth at which the drill string may assume itssubstantially true vertical position throughout this section ofv thebore hole. The diameter of such a slot isnormally approximatelythat ofthe diameter'of any tool joints on the section of the drill pipe Whichengages in this cutting action, and generally tapers outwardly towardsits oppositeendsiwhere it merges with the straight sections of the borehole. The slot thus'cut is commonly called in, the industry a keyseat'and is a very common occurrence, particularly in the drilling ofdeep wells, and its presence is normally not. apparent to the drilleruntil he attempts to Withdraw the. drill. string from the well.

When a drill string has out such a key seat along a bore hole, it willbe seen that its smallthe well is normally done at relatively highspeed,

the string may thus become stuck in the key seat and cause the attendantdifficulties resulting from such an accident. It is possible, however,

that the presence of such a key seat may become known to the drillerthrough the actions of the drill and by carefully withdrawing the drillstring, while rotating it, it may be possible to work the drill stringaround through the curved portion of the drill hole and avoid stickingthe drill string in the manner described. However, this is a relativelyfortuitous circumstance, since the more common situation is that thepresence of a key seat is not initially discovered until the drillcollar has become stuck.

Whenever the bit section becomes stuck in a key seat or for otherreasons, various expedients may be employed in an effort to releasethem. For example, a quantity of oil may be pumped down the drill stringand up around the outside of the bit section in an effort to provide adegree of lubrication which will efiect its release. These expedientsgenerally take time to efiectuate, even if they prove successful. Duringsuch time mud circulation is generally continued in order to preventsettling of cuttings and sloughing of the material lining the bore holewhich would otherwise aggravate the difliculty. However, rotation of thedrill during this period cannot generally be continued due to the dangerof twist-offs and the inability to rotate the drill string may aggravatethe conditions causing sticking despite the continuation of mudcirculation.

Once it becomes evident that the bit section cannot be released by wayof the conventional expedients, it then becomes necessary to break thedrill stem, preferably at a point as close as possible to the point atwhich the drill is stuck, so that the greatest possible length of drillstring may be withdrawn from the well, leaving a minimum amount ofequipment to be recovered by conventional fishing operations. Thisbreaking of the drill string may be accomplished by reversing thedirection of rotation of the rotary table to unscrew the drill stem orby shooting off the drill stem with explosives placed as near aspossible to the point of sticking. However, although some degree ofcontrol may be exercised as to the point at which the drill string willunscrew or the shot may be placed, the results are uncertain, at best,particularly since such operations are generally a matter of last resortafter all other expedients designed to release the drill have been triedwithout success. During the time required to exhaust all otherexpedients, the bore hole above the original point of sticking may bedamaged or otherwise so affected that it may no longer be possible toget close to the sticking point with the final breaking operations andmuch greater portions of the drill string must then be left in the holefor removal by fishing or other operations conventionally employed toclear the bore hole.

It is a principal object of this invention, therefore, to provide a toolfor rotary drilling which will obviate or eliminate one or more of thedifficulties, such as those described above, which are commonlyencountered in rotary drilling.

Other important objects of this invention are to provide a tool forstabilizing the drill collar to reduce the eccentric or gyratory motionthereof to a minimum; to aid in releasing the drill string when it hasbecome stuck in a key seat or other obstruction in the bore hole; and incases where permanent sticking of the bit section has occured, to effecta break in the drill string so as to recover the maximum length of thedrill string leaving a relatively minor portion to be recovered bysubsequent fishing operations.

Other objects of this invention are to provide a rotary drilling toolwhich is adapted to be inserted in the drilling string adjacent a drillcollar and which is provided with a longitudinally slidable androtatable section which functions as a stabilizer for the drill collarwhile, at the same time, permitting a degree of longitudinal androtational movement of the drill string relative thereto; and which isprovided with a clutch mechanism by means of which a controlled breakingof the drill string may be effected if desired.

Other and more specific objects of this invention will be apparent fromthe following detailed description when read in conjunction with theaccompanying drawings which illustrate useful embodiments in accordancewith this invention.

In the drawings:

Fig. 1 is a partly diagrammatic view of a portion of a bore holeillustrating the position and form of a key seat in such a bore hole andshowing the position of the drill string, including a tool in accordancewith this invention, in position in the bore hole;

Fig. 2 is a cross-section taken along line 22 of Fig. 1;

Fig. 3 is an elevational view, partly in section, of a tool inaccordance with one embodiment of this invention;

Fig. 4 is a cross-section taken along the line 44 of Fig. 3;

Fig. 5 is a view of a portion of the tool in accordance with anotherembodiment of this invention.

Fig. 6 is a view of a portion of the tool in accordance with stillanother embodiment of this invention.

Referring to the drawings and to Figs. 3 and 4 in particular, whichillustrate one useful embodiment in accordance with this invention, thedevice consists of a generally tubular body member ll having a bore Hand provided with an internally threaded box l2, adapted for connectionto the threaded pin 13 of a tool joint l4, which is a part of aconventional drill stem l5 (Fig. l), the bore H of the device being ingeneral alignment with the bore of the tool joint and its connecteddrill stem. The diameter of body In is preferably made equal to orslightly greater than that of tool joint M, the upper end of body It!being tapered at Ifia to the diameter of the tool joint. Beginning at apoint spaced from the upper end of body Ii), the exterior of the body isreduced in diameter throughout the remainder of its length, forming ashoulder It at an intermediate point along body H]. The portion ofreduced diameter of the body, termed the mandrel, is designated by thenumeral I1, and at its lower end is provided with a tapered threaded pinl8 for attachment thereto *of a tubular sub 1 9 having= a complementarythread'edboX 25 for reception of pin 1-8. The lower end or sub 9 isprovided-with athreaded'pin 2 l, which isadapted for connection into abox 22 of a conventional d-rill collar 23. "The outsidediameter of subl9is" generally made the-same as that of drill collar23- and botharetherefore, substantially larger indiameter than tool joint M and bodyIn. Slidably mounted on mandrel I1 is a generally-cylindrical' sleeve,termed a stabilizer 24, constructed' of" Duprene, rubber,-or otherresilient plastic" material which 'is preferably .resistant to theactiono'f oil and other w'elYfluids. -Stabilizer '24 ispreferably'molded about a'met'al reinforcing sleeve-25', which forms acore for "the stabilizer,-an'd-is provided-with a plurality ofperforations 26 for assistance in' anchoring-the plastic materialthereto. Reinforcing-sleeve is; provided at itsupper andlower-ends,-which extend beyond the ends of the body'of plastic materialattachedthereto, with outwardlyextending generally annular flanges'fland*28, respectively, the outer diameters of which are substantially equalto that'of sub l9. W-ith this reinforcing arrangement, stabilizer 24'becomes a relatively rigid member so far as resistance to longitudinalpressure is concerned. "The exterior surface of stabilizerMus-preferably formed in molding toprovide "a series'o'f uniformlyspaced longitudinalribs" 29- thereonwhichextend radially outwardlyfromthe periphery of the stabilizer; "The'radial' length of ribs" 29*"ispreferably such that the diameter of a circle en'- compassing theouter-edges thereof which='wil1 begreater than that of thedr'ill' collarand 'sub "l9, and which'will be almost equal to "the diameter of theboreh01e,so*that the stabilizer will offer no appreciable resistance tothemov'e- -ment of the drill stringin 'the'bore-hole-under in contact,the teeth will becomeengaged only J when sub 19 andthe drill stem, towhich itis attached, are rotated in the counter-clockwise direction,that is counter to 'thedirection of rotation for "normal drilling. Theover-all length of stabilizer 24, including teeth 32 =and flange 2-1.is" made less than the length ofmandr'el :1 between shoulder 16' and theupper edges of teeth-33' of the sub, whereby adeg-ree of-'longitudinalmovement of stabilizer 24 on mandrel H may occur. A suitable degree ofclearance 'isalso provided between the inner surface'of stabilizer Mrandthe outer surface of mandrel l! to provide free relative rotational andlongitudinal movement between these members.

Shoulder IS and theupper edge of sub llf'form stop: means to' limitthelongitudinal movement of: stabilizer 24 relative to the drill string.

The device of this invention is employed in rotary drilling in thefollowing manner:

The tool of this invention is inserted'in a' .drill'string between thelower end'of-drill stem and the upper endof drill collar" 23,'theLlatterhaving' a conventional bit 34 I attached to the lower endthereof-I .As drillin'g'proceeds, cutting .theibore': hole; 35n'with2adiameter;substantially the same asthat of the cutting-edges "o'fthe bit,the tool will move downwardly through-the bore hole following'the" bit.Stabilizer 24 will act to stabilize the bit section,--since the ribs'29- -th'ereon-will bridge-the" annular space between the wali' Of'thebore hole and the outside of the; drill collar and" forma type of sleevebearing for theupper end or the drill collar which will,thereforepreduceithe tendency of -the upperend of the drill-collar toengage in any eccentric-or gyratory*movement. When made of resilientmaterialgas described, stabilizer 2 willalso' absorb-the-shock of" anysuch'movementagainst the wall of -'-the-= well bore; the ribbedconfiguration affording a degree of resilient flexingundersuch-=movement,=and this will further aid in preven'ting-thedrilF-collar' from digging into I -drill"string is being" rotatedinthe-normal or clockwise'di-rection. In this event; the -teeth 33 onsub-"lw'ill merely roll under and past teeth 32. I-nter-locking-of theteeth"- will be effected -i-n-"the manner I described hereinafter.

Should the "bitsection-become stuck in the borehole; asmayoften occur,so that-it cannot be withdrawn" from the well without placing-unduestrainon the drill string, the" sl-idable a!- rangement or stabilizer 24on-mand-rel l 'Imay be utilizedto employ the tool as a setof jars-tofree the bit" section: '-"I-his= may-be accomplished by applyinganupward pull" on the drill" stemby -mean's-*of-'the' conventional drawworks (not shown), at the' top 'of the well until the drillstem;"-because'--of its naturarelasticity, is" in'increasd-tvAhsidn.Then the" drill string "is quickly released and then caught afterashort-interval.

"These actions will transmit an energy wave down the drill stem andproduce'a'sharp impact between shoulder -|6*o'f body I0 and theupperedge of flange" 2T. This will produce a jarring efiect 'on"='the'bit section, particularly since itis relativel'y closeto' th-pcintof'impact; and willloosen the bit' section. This jarring action may be re---peated= as often as necessary to free the bit.

When conditions *in the bore hole become-such as will normally cause 1the bit to become stuck, whetherit-bean unusual degree of settling ofcuttings,- sloughing of material'from' the wall of the bore holeythepresence of key seats or other obstructionss'stabilizer 24-;since it isthe portion-of "the drill string, other than the. bit itself," havingthe" largest diameter, will'normallybecome stuck -first in anyobstruction whichwould not pass the-bit se'ctiomand this will occurgenerallybefore the bit sectionitself becomes stuck too tightly -to-respor'id to'rotationof t-he drillstem. Rotation of the bit sectionmay, therefore-, be continued by means of' this' tool =Whi1e operationsare G'OhdlIGtQd'tU ffIBG CHG drill string; as by'efiec'tin'g the jarringaction described above.

' Wham-a key seat form's the principal: obstruc= ztion to' the" removal.of. thef-d rill string, stabilizer 24 will be the portion which willfirst become stuck therein as the drilling string is drawn upwardlytherethrough. When this occurs, the tools may often be jarred loose inthe manner previously described and the presence of a key seat beingthus disclosed, it then becomes possible for the driller, by carefullycontrolling the rate of withdrawal of the drill string and by continuingits rotation, to work the string around the key seat through the borehole proper and thus withdraw the tools. Here again the presence of thestabilizer 24 in the drill string, which permits the driller to maintainrelatively free rotation of the string, is of great assistance in theseremoval operations.

In a case, however, where stabilizer 24 becomes so stuck in the borehole that the tools cannot be released by any of the previouslymentioned expedients and it then becomes necessary to break the drillstring, the tool in accordance with this invention may be employed toeffect the break in the following manner:

An upward pull will be applied through the draw works to the upper endof the drill string which will draw the lower end thereof, comprisingmandrel ll, sub l9, drill collar 23 and bit 34, upwardly throughstabilizer 24 until teeth 33 on sub l9 engage teeth 32 On the lower endof stabilizer 24. lhe rotary table is then rotated in thecounter-clockwise direction to similarly rodrilling art, the drill stemcan generally be caused i to back-oil at a point very close to theportion thus held stationary, with the result that maximum lengths ofthe drill string can thus be readily recovered without serious damage,generally leaving only the stabilizing tool and bit section to beremoved by the subsequent fishing or other well known operation employedto clear the hole.

Such fishing operations will also be substantially aided by the form ofthe stabilizer 24. Where the latter is constructed of relatively softplastic material, whether or not the rib-type configuration is employed,it becomes relatively easy, when a conventional reaming cutter is runinto the well, to ream olf the relatively soft material composing thestabilizer to the point where conventional hollow fishing tools mayeasily pass over the outside of the remainder of stabilizer 24 to reachand grasp the drill collar.

Instead of constructing stabilizer 24 of resilient or plastic material,as described, stabilizer 24 may be constructed of steel or other metalhaving ribbed configuration similar to that described. In

"this case, the stabilizer will retain the stabilizing I a Fig.illustrates another formof stabilizer which may be successfully employedwith the tool of this invention in place of stabilizer 24. In thisembodiment a stabilizer 3B, which may be zconstrueted of resil or psticma ri lsio the type previously described or of steel or othermetals, as may be desired, is slidably mounted on mandrel l'l. Insteadof an external ribbed configuration, as in the previously describedembodiment, stabilizer 3B is provided with a smooth exterior and aplurality of circumferentially spaced longitudinal passageways 39, whichextend through the body of the material between the inner and outersurfaces thereof for passage of drilling fluid therethrough. Since muchof the material forming the body of stabilizer 38 will be removed inproviding passageways 39, this embodiment, even when constructed ofmetal, can be ground or reamed off when necessary without unduedifliculty. In substantially all other respects, this embodiment willfunction just as that previously described and will retain theadvantageous features thereof.

Fig. 6 illustrates still another embodiment in accordance with thisinvention in which flange 28 and the upper end of sub i9 are providedwith teeth elements 40 and 4|, respectively, which are of substantiallysquare shape or of other suitable configuration such that, when broughtinto interengagement by an upward pull on the drill string, clutchingengagement of stabilizer 24 with the drill string will be effected,irrespective of the direction of rotation of the drill string. Such anembodiment is particularly useful in connection with the millingoperation described above. In this operation by clutching the partstogether while rotating slowly in the normal or clockwise direction, arotational component may be imparted to the reciprocatory movement ofstabilizer 24 which w ll aid the millin p nhis embodiment may also beemployed for the unscrewing or backing-off operation previouslydescribed, when necessary or desirable, by rotating the drilling stringin the counter-clockwise or anti-normal direction While the teeth areheld in inter-engagement by an upward pull applied to the drill string.

It will be understood that the dimensions of the parts of the device inaccordance with this invention may be varied depending primarily on thesize of the drill bit and drill collars employed. The degree oflongitudinal movement of the stabilizer on mandrel I7 is likewisevariable but, in general, only a few inches of such movement is all thatis necessary. Merely by way of illustration, in the case of a 12-inchstabilizer, the degree of longitudinal movement may be about eighteen totwenty-four inches to enable the device to successfully accomplish itsseveral functions.

It will be understood that while the device in accordance with thisinvention is preferably employed by inserting it in a drill stringimmediately adjacent the upper end of the bit section, it may beemployed successfully by inserting it between sections of a drillcollar, and in some cases may be spaced above the end of the uppermostdrill collar.

Various alterations and changes may be made in the details of the devicein accordance with this invention within the spirit of this inventionand without departing from the scope of the appended claims.

What we claim and desire to secure by Letters Patent is:

1. A drill collar stabilizer comprising, a tubular body member adaptedto be inserted in a drill string adjacent a drill collar, said bodymember having a portion of reduced diameter intermediate its endsgtoform an upper stop member on said body member, a tubular sub connectedto the lower end of said body forming a lower stop member, a tubularsleeve member rotatably mounted on said portion of reduced diameter andslidable thereon between said stop members, cooperating clutch meansarranged between the lower end of said sleeve member and the lower oneof said stop members engageable only upon upward movement of saidtubular body relative to said sleeve member to effect clutchingengagement thereof, a

plurality of angularly spaced vertically extending ribs on the exteriorof said sleeve member, the external diameter of said sleeve memberincluding said ribs being greater than that of said drill collar, saidtubular sleeve member including said ribs comprising a generally tubularbody constructed of resilient rubber-like material mounted upon atubular metallic core, the ends of which extend beyond the ends of saidbody of resilient material, laterally extending flanges on the oppositeends of said core, the upper one of said flanges cooperating with theupper one of said stop members for efiecting jarring impacttherebetween, and the lower one of said flanges carrying one of saidclutch members.

2. A rotary drill stabilizer comprising, a tubular body insertible in adrill string, a first stop member mounted at an intermediate point onsaid body, an enlargement forming a second stop member connected to saidbody below said first stop member, a tubular sleeve member rotatably andslidably mounted on said body between said stop members, said sleevemember comprising a tubular metallic core, laterally extending flangeson the opposite ends of said core, a generally tubular memberconstructed of resilient rubberlike material mounted on said corebetween said flanges and having a plurality of angularly spacedlongitudinal ribs projecting radially from the exterior surface thereof,and cooperating clutch elements mounted on the lower one of said flangesand the adjacent stop member engageable upon upward movement of saidtubular body relative to said sleeve member.

CICERO C. BROWN. FRED F. WALTERMIRE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,072,320 Thomas Mar. 2, 19372,166,937 Bettis July 25, 1939 2,177,300 Kellegrew Oct. 24, 19392,323,027 Gerstenkorn June 29. 1943

